1. Field of the Invention
This invention relates to machine tool apparatus, and particularly to apparatus for a stress-free holding of a part for machining.
2. Description of the Prior Art
A machine tool apparatus of the kind to which this invention relates provides a fixture into which a part or a work piece is clamped and held while one or more machining operations is performed thereon. When plural machining operations are required, the part is released, repositioned so that a first machined surface thereon properly contacts a machine reference surface, and then again clamped in the fixture so that a second machining operation can take place, which operation is precisely related to the first. In the case of irregularly shaped precision castings, and other not inherently rigid parts, adjustment of the fixture to re-clamp a reference surface positioned part may distort the part causing a second machined surface not to have the relationship to the first machined surface required by part design. Efforts have been made to deal with this problem by relatively elaborate arrangements of independent clamping devices involving multiple individual adjustments. As known, prior art arrangements yield inconsistent results, related largely to the skill of the adjuster, and in any event substantially increase the labor time involved in producing a machined part. A concept of a fixture adjustable to conform to part configuration and location, without applied stress, is unknown in the prior art as is a concept of a single means locking the fixture against motion in plural senses after it has been adjusted to and clamped to the part.